In early 1987, it was discovered that YBa.sub.2 Cu.sub.3 O.sub.7 material (in the form of a ceramic) becomes superconducting at a relatively high cryogenic temperature, which is desirable. However, it was soon learned that YBa.sub.2 Cu.sub.3 O.sub.7 material suffers from a major problem. Specifically, if a volume of bulk YBa.sub.2 Cu.sub.3 O.sub.7 material is exposed to water (H.sub.2 O), either by immersion or by contact of its surface with moist air, YBa.sub.2 Cu.sub.3 O.sub.7 chemically reacts with such water and thereby tends to lose its superconductive qualities. The present invention overcomes this problem.